This invention generally relates to geographic location determination. More specifically, this invention relates to geographic location determination via a cellular telephone.
In the near future cellular telephones will have the capability to make a geographic location determination. Many methods have been proposed to implement the location determination feature in a cellular telephone. One method is to integrate a Global Positioning System (GPS) receiver in the cellular telephone. The GPS receiver periodically receives timing signals from GPS satellites and processes the timing signals to make a location determination.
Under various conditions, GPS receivers have significant trouble receiving the necessary satellite timing signals. For example, if a user is inside a building, the GPS signals may not be strong enough for the user""s GPS receiver to detect the signals. The GPS signals may become even weaker (e.g. more difficult to detect) as the cellular telephone is deeper within a building and away from any windows. In this situation, the cellular telephone GPS receiver would continually check for the GPS signals, and this continuous xe2x80x9ccheckingxe2x80x9d can significantly drain the cellular telephone battery. The same problem may be encountered if other position location technology (e.g. triangulation) is employed. Therefore, there is a need for a method and apparatus for making location measurements via a cellular telephone without unnecessarily draining the battery power of the cellular telephone.